/*******************************************************************************
 * Copyright 2011 See AUTHORS file.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 ******************************************************************************/

package com.badlogic.gdx.math.collision;

import com.badlogic.gdx.math.Matrix4;
import com.badlogic.gdx.math.Vector3;

import java.io.Serializable;

/**
 * Encapsulates a ray having a starting position and a unit length direction.
 *
 * @author badlogicgames@gmail.com
 */
public class Ray implements Serializable {
    private static final long serialVersionUID = -620692054835390878L;
    static Vector3 tmp = new Vector3();
    public final Vector3 origin = new Vector3();
    public final Vector3 direction = new Vector3();

    /**
     * Constructor, sets the starting position of the ray and the direction.
     *
     * @param origin    The starting position
     * @param direction The direction
     */
    public Ray(Vector3 origin, Vector3 direction) {
        this.origin.set(origin);
        this.direction.set(direction).nor();
    }

    /**
     * @return a copy of this ray.
     */
    public Ray cpy() {
        return new Ray(this.origin, this.direction);
    }

    /**
     * Returns and endpoint given the distance. This is calculated as startpoint + distance * direction.
     *
     * @param distance The distance from the end point to the start point.
     * @return The end point
     */
    public Vector3 getEndPoint(float distance) {
        return new Vector3(origin).add(direction.tmp().mul(distance));
    }

    /**
     * Multiplies the ray by the given matrix. Use this to transform a ray into another coordinate system.
     *
     * @param matrix The matrix
     * @return This ray for chaining.
     */
    public Ray mul(Matrix4 matrix) {
        tmp.set(origin).add(direction);
        tmp.mul(matrix);
        origin.mul(matrix);
        direction.set(tmp.sub(origin));
        return this;
    }

    /**
     * {@inheritDoc}
     */
    public String toString() {
        return "ray [" + origin + ":" + direction + "]";
    }

    /**
     * Sets the starting position and the direction of this ray.
     *
     * @param origin    The starting position
     * @param direction The direction
     * @return this ray for chaining
     */
    public Ray set(Vector3 origin, Vector3 direction) {
        this.origin.set(origin);
        this.direction.set(direction);
        return this;
    }

    /**
     * Sets this ray from the given starting position and direction.
     *
     * @param x  The x-component of the starting position
     * @param y  The y-component of the starting position
     * @param z  The z-component of the starting position
     * @param dx The x-component of the direction
     * @param dy The y-component of the direction
     * @param dz The z-component of the direction
     * @return this ray for chaining
     */
    public Ray set(float x, float y, float z, float dx, float dy, float dz) {
        this.origin.set(x, y, z);
        this.direction.set(dx, dy, dz);
        return this;
    }

    /**
     * Sets the starting position and direction from the given ray
     *
     * @param ray The ray
     * @return This ray for chaining
     */
    public Ray set(Ray ray) {

        this.origin.set(ray.origin);
        this.direction.set(ray.direction);
        return this;
    }
}
